Crimped electrical connector terminals are conventionally known, and often fabricated using the same conducting material for the crimp barrel and the conductors of the wire. Commonly, the conducting material is copper, due to its good electrical conductivity and mechanical strength. However, copper has nevertheless some drawbacks. Firstly, the price for copper has risen sharply in recent years. Secondly, copper is relatively dense, making it a heavy material. There is an increased industrial effort to both reduce the cost, and the weight of automobiles. Such efforts would benefit greatly by exchanging the rather heavy copper with more lightweight materials.
Given aluminium's good electrical conductivity, in combination with light weight and low cost, aluminium has been identified as a suitable material to reduce the use of copper conductors. It has long been proposed to produce electrical terminals with aluminium conductors that are crimped to a copper connector. Such a combination would thereby combine the light weight of aluminium conductors with the good spring characteristics of copper. However, the use of aluminium in combination with copper is challenging. In the presence of moisture, a difference in potential between copper and aluminium will result in the dissolution of aluminium at the points of contact between aluminium and copper, thereby negatively effecting the electrical connection between the two materials. To overcome this problem, measures have to be taken to prevent the presence of moisture in the contact area.
One such approach is disclosed in International Patent Publication No. WO 2012/054072, which discloses an electrical terminal using a copper-aluminium combination. The electrical terminal uses an F-crimp that extends from the stripped conductors of the wire up until a segment of the wire where the conductors are surrounded with an insulation layer. The crimp barrel has a front sealing portion for closing gaps at the extremity of the stripped conductor. Thus, moisture may be prevented from reaching the contact between the aluminium conductor and the copper crimp barrel. However, such a design presents sever disadvantages.
First, since the additional front seal segment is also crimped with an F-crimp, just like the other segments of the crimp barrel, the entire electrical terminal is longer in length than conventional terminals using only copper for both the wire and the crimp barrel. The extra length may result in an incompatibility with existing copper-based cable harnesses having copper terminals, when the copper-based cable harnesses are exchanged with an aluminium cable harness having the copper-aluminium terminals.
Furthermore, due to the lower conductivity of the aluminium with respect to copper, the diameter of the conductors of an aluminium wire has to be larger than the diameter of an equivalent copper wire. To avoid increasing the total diameter of the wire, the thickness of the insulation layer is typically made smaller. This, however, leads to an increased risk of moisture penetrating to the contact areas in regions where the insulation layer around the conductors is accidently cut during the crimping process. Thus, there is a higher risk that the aluminium conductors may become exposed to moisture in contact areas with copper, negatively effecting the lifetime of the connector.
In another approach, detailed in U.S. Pat. No. 4,641,911, an electrical terminal has a crimp barrel positioned such that both the stripped conductors and the insulation is crimped. A funnel shape is formed in the axial direction by partially overlapping the sidewalls of the crimp barrel. However, the crimp barrel is not suited for copper-aluminium connectors, as in the transition region between the stripped conductors and the insulation layer of the wire, the crimp barrel is not closed so that moisture can easily penetrate to the contact area.
Therefore, there is a need for an electrical terminal with an improved crimp barrel to reduce the risk of exposure of the contact area to moisture, where the electrical terminal has a reduced length so as to be compatible with conventional copper-based electrical terminals.